package com.huixuebao.common.util;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

@Slf4j
public class RSAEncrypt {

    //用于保存公钥与私钥
    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();

    public static void main(String[] args) throws Exception {
        //生成密钥对
        genKeyPair();
        //加密字符串
        String message = "hand-llq-25404hand-llq-25404hand-llq-25404hand-llq-25404hand-llq-25404hand-llq-25404";
        System.out.println("公钥为:" + keyMap.get(0));
        System.out.println("私钥为:" + keyMap.get(1));
        System.out.println("加密前的字符串为:" + message);
        String messageEncryption = encrypt(message, keyMap.get(0));
        System.out.println("加密后的字符串为:" + messageEncryption);
        String messageDecrypt = decrypt(messageEncryption, keyMap.get(1));
        System.out.println("解密后的字符串为:" + messageDecrypt);
    }

    /**
     * 生成密钥对
     * @throws NoSuchAlgorithmException
     */
    public static Map<String, String> genKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器，密钥大小为512位(密钥长度最小为512位)
        keyPairGen.initialize(1024);
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        //获得私钥
        RSAPrivateKey privateKey = (RSAPrivateKey)keyPair.getPrivate();
        //获得公钥
        RSAPublicKey publicKey = (RSAPublicKey)keyPair.getPublic();
        //得到公钥字符串
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        //得到私钥字符串
        String privateKeyString = new String(Base64.encodeBase64(privateKey.getEncoded()));
        //将公钥和私钥保存到Map 0表示公钥 1表示私钥
        keyMap.put(0, publicKeyString);
        keyMap.put(1, privateKeyString);
        log.info("publicKeyString {}", publicKeyString);
        log.info("privateKeyString {}", privateKeyString);
        Map<String, String> result = new HashMap<>();
        result.put("publicKey", publicKeyString);
        result.put("privateKey", privateKeyString);
        return result;
    }

    /**
     * RSA公钥加密
     * @param message   需要加密信息
     * @param publicKey 公钥
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String message, String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
                .generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.encodeBase64String(cipher.doFinal(message.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     * @param message    需要解密信息
     * @param privateKey 私钥
     * @return 明文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String message, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(message.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
                .generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }
}
